Date Range:

Friday, July 13, 2012 to Monday, July 16, 2012

Publication Date:

2013

Methods:

The LTER moist acidic tussock (Toolik MAT) site was set up in 1989. The experimental design is four blocks of 5 x 20 meter plots with randomly assigned treatments within each block. Treatments include control (CT), nitrogen (N), phosphorus (P) and nitrogen plus phosphorus (NP). Fertilizer is added annually following snowmelt in June as 10 g/m2 nitrogen (as NH4NO3) and 5 g/m2 phosphorous (as triple superphosphate). Exclosure plots were set up at the MAT site in July 1996 on extra 5 x 20 meter plots within the four-block design of the 1989 LTER acidic tussock experimental plots. On each plot a 5 x 10 meter section was fenced with large mesh (4-inch square mesh) and within this fence a 5x5-meter plot was fenced with a small mesh (1/2-inch square mesh). In each block two fenced plots were setup: a plot with no fertilizer and a plot with annual fertilization treatments as described above. Thus the treatments created are no fence, no fertilizer (NFCT); small mesh fence, no fertilizer (SFCT); large mesh fence, no fertilizer (LFCT); no fence, N plus P (NFNP); small mesh fence, N plus P (SFNP); and large mesh fence, N plus P (LFNP). Only NFCT, NFNP, SFCT, and SFNP were censused in 2004. The LTER dry heath (Toolik DH) site was also established in 1989 using the same methods at MAT in three block replicates. Exclosure plots were set up in 1996 using the same methods at MAT. In 1997 experimental plots were established at the LTER moist non-acidic tussock (Toolik MNT) site with the same methods as those used at MAT. CT, N, P and NP treatments are replicated in three blocks at MNT.Calculations: All percent cover values were summed within each plot, and then each value was divided by the total to generate a percent cover value standardized to 100%. Reference Citations: Gough, L. and S.E. Hobbie. 2003. Responses of moist non-acidic arctic tundra to altered environment: productivity, biomass, and species richness. Oikos 103:204-216.Gough, L., P.A. Wookey, and G.R. Shaver. 2002. Dry heath arctic tundra responses to long-term nutrient and light manipulation. Arctic, Antarctic, and Alpine Research. 34: 211-218.Shaver, G.R., J.A. Laundre, A.E. Giblin, and K.J. Nadelhoffer. 1996. Changes in live plant biomass, primary production and species composition along a riverside toposequence in Arctic Alaska, U.S.A. Arctic and Alpine Research. 28: 363-379.Sampling Description.Permanent monitoring areas were established in all treatment plots in 1998. Eight 1 m2 plots are sampled in each treatment in each block each year at the end of July. A 1 m2 quadrat is aligned 0.2 m inside of the plot at the site of a flag marking the first measurement. Within this quadrat, aerial percent cover of all vascular plants are noted by species as is all other ground cover. Categories include moss (all species lumped), lichen (all species lumped), litter, and standing dead Betula nana. Bare ground, frost boil, and water are also recorded. As an indicator of vole activity, the percent cover of the plot comprised of vole burrow holes, vole trails, and vole litter (small pieces of dead plant material) are also recorded. To standardize cover among plots, all percent cover values were summed within each plot, and then each value was divided by the total to generate a percent cover value standardized to 100%.

In 2006, a new set of experimental treatments were established in MAT near the earlier plots described above. These include a gradient of fertilization treatments that receive nitrate or ammonium alone, or receive N and P additions with 0.5, 1, 2, 5, or 10 g N added with half of that amount added as P. An additional set of plots were set aside upon establishment for future experiments, and are noted as H. We sampled from blocks 1-3 in 2008 from the following treatments: 06CT, 06F0.5, 06F1, 06F2, 06F5, 06F10, 06NO3, 06NH4, 06H.

Variable Details

(Variables names are in the first line/row of the CSV file and Excel data sheet.)

Year

Label: Year

Definition: The year of percent cover measurement.

Type: Date/time

Date format: yyyy

Missing values: None specified

Site

Label: Site

Definition: The site of percent cover measurement

Type: Nominal

Missing values: None specified

Treatment

Label: Treatment

Definition: The manipulated treatment

Type: Nominal

Missing values: None specified

Block

Label: Block

Definition: The treatment block number

Type: Nominal

Missing values: None specified

Plot

Label: Plot

Definition: Sample plot where precent cover was measured

Type: Nominal

Missing values: None specified

Species

Label: Species

Definition: Species and cover categories determined on plots as described above

Type: Nominal

Missing values: None specified

Relative Cover

Label: Relative Cover

Definition: The percent cover of a given species relative to the total cover of the plot

Type: Physical quantity

Unit: percent

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values: None specified

This material is based upon work supported by the National Science Foundation under Grants #DEB-1637459, 1026843, 9810222, 9211775, 8702328; #OPP-9911278, 9911681, 9732281, 9615411, 9615563, 9615942, 9615949, 9400722, 9415411, 9318529; #BSR 9019055, 8806635, 8507493. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.